[holdynx]

Hey guys! I am currently working on a lab report but I do not understand the following questions listed below. Hopefully I can get some help with those questions.

We have performed an acid-base titration using NaOH [0.1 M] and an unknown weak acid (HA). The acid is diluted (1:10, as written below). After the titration we calculated the diluted [acid] (by v * c = v * c) to be 0.101 M. Here are the questions asked regarding the lab:

1: What is the molar mass of the unknown acid HA when 59.5g of the acid was added to 1 liter of water before dilution (25.0mL pipetted into an Erlenmeyer flask and diluted with water to 250mL).

2: What is the unknown acid HA? (The molar masses calculated in problem 1) and with a pKa of ca 4.7?

Thanks in advance!

[chenbeier]

What was the consumption of 0,1 M NaOH by titrating the 25 ml of the acid. The 250 ml dilution doesn't matter. This consumption gives the mole of NaOH, and calculated with the 1 protonic acid volume its molarity. Was 0,101 M your result? The make up was 59,5g/l.

With n= m/M  you can calculate M = m/n

But where did you do the 1:10 dilution. This has to be done before you add 25 ml in the erlenmeyer.
Normally a measured flask has to be taken. 25 ml in 250 ml accurate. Then from this 25 ml are taken for titration.